The invention relates to an optoelectronic component having a radiation-receiving or radiation-emitting semiconductor chip, which is fastened to or on a base part and is connected to at least two electrode terminals made of an electrically conductive material. The electrode terminals serve to electrically contact the component. The invention furthermore relates to a method for producing such an optoelectronic component.
Optoelectronic semiconductor components of this type are mass-produced. They serve as transducers to convert optical signals or energy into electrical signals or energy, or vice versa. Radiation receivers or radiation-sensitive components are, for example, photodiodes or phototransistors. Transmitters or radiation-emitting components include (visible) light-emitting diodes (LED) and infrared radiation-emitting diodes (IRED). These optoelectronic components are expediently produced in the wafer composite and, after completion, are separated from the wafer composite in the form of parallelepipedal chips. Depending on the purpose of use, the finished semiconductor chips are then fastened to a suitable carrier, contact-connected and embedded in an encapsulation made of transparent plastic. In addition to affording protection for the semiconductor chip as well as the contact wires, the plastic encapsulation is additionally ascribed the function of improved radiation input coupling and radiation output coupling in and on the chip.
In addition to the ubiquitously known radial designs with a plastic housing and elongate electrode terminals which is protrude to one side, designs of light-emitting diodes which are also suitable, in particular, for surface mounting are known, in which a so-called lead frame is provided as a prefabricated carrier part for the semiconductor chip, and the electrode terminals are small legs that are routed laterally from the plastic housing and bent. In the course of producing such LEDs for surface mounting, an endlessly stamped conductor strip is encapsulated by injection molding with a thermoplastic which is resistant to high temperature. In a further method technique, the light-emitting diode is fitted into a holder suitable for surface mounting only after the potting fabrication. German published patent application DE 31 28 187 A1 discloses an optoelectronic component. The component has a radiation-receiving or radiation-emitting semiconductor chip fastened to a base part and connected to two electrode terminals. The two connections are applied in a planar manner to the carrier, are connected to the semiconductor body and extend from that outer surface of the carrier which carries the semiconductor body as far as at least one further outer surface of the carrier, where they form a connection contact area.
German published patent application DE 19 21 124 A1 discloses an optoelectronic transducer with a semiconductor chip fastened to a carrier unit. The carrier unit has a chip mounting region which is assigned a number of connection parts. These connection parts are provided with electrical connection areas which define a plane whose spacing from the chip mounting region is greater than the maximum height of the semiconductor chip, if appropriate including all the connecting conductors and/or covering means referring to the chip mounting region.
Japanese J. Appl. Physics, Vol. 27, 1988, pp. L1764-L1767 discloses a method in which an insulating substrate is covered with a thin coating of copper by means of deposition from a liquid chemically and without the action of an external current flow, i.e. by electroless plating. The copper coating is then etched selectively with the aid of photolithography, a mask layer being deposited and patterned. As a result, regions of the coating which are not covered and those which are covered by the mask material are identified, and the regions which are not covered by the material of the mask layer are selectively removed by means of etching.
It is accordingly an object of the invention to provide an optoelectric component and production method, which overcomes the disadvantages of the heretofore-known devices and methods of this general type and which specifies an optoelectronic component, in particular SMT optocomponent (SMT=Surface Mounted Technology) and a method for its production which, with an even further reduced structural size of the component, enables cost-effective production in particular in conjunction with high numbers, even with different designs.
With the foregoing and other objects in view there is provided, in accordance with the invention, an optoelectronic component, comprising:
a base part having outer surfaces;
a radiation-receiving or radiation-emitting semiconductor chip mounted on the base part;
at least two electrode terminals of electrically conductive material connected to the chip and extending on the outer surfaces of the base part, the electrode terminals being formed by a patterned, thin coating on the outer surfaces of the base part.
In accordance with an added feature of the invention, the surfaces of the base part include a top side facing the semiconductor chip, an underside opposite the top side, and edge portions between the top side and the underside, and wherein the electrode terminals extend from the top side of the base part, across the edge portions and to the underside of the base part.
In accordance with an additional feature of the invention, the underside of the semiconductor chip is seated on one of the electrode terminals.
In accordance with another feature of the invention, the base part is provided with a heat sink of thermally conductive material that is in thermal contact with the semiconductor chip.
With the above and other objects in view there is also provided an improved method of producing an optoelectronic component of the type described above. The improvement comprises the step of coating outer surfaces of the base part with a thin layer of electrically conductive connection material, and patterning the coating to form the electrode terminals.
In accordance with a further feature of the invention, the method comprises:
covering the base part with a thin coating made of the electrically conductive connection material by deposition from a liquid;
patterning the thin coating so as to form individual regions of the coating that are electrically insulated from one another;
selectively depositing a further thin layer of auxiliary material on a number of predetermined regions of the thin coating by electrodeposition with external electric current, for increasing a layer thickness of the thin coating at the predetermined regions; and
selectively removing regions of the thin coating on base part that have not been thickened in the depositing step by means of etching.
In accordance with again a further feature of the invention, the covering step comprises depositing the thin coating chemically and without an external electric current. In accordance with again an added feature of the invention, the patterning step comprises patterning the mask layer with a beam selected from the group consisting of a light beam, a particle beam, and a laser beam.
In accordance with again an additional feature of the invention, the removing step comprises removing the non-masked conductive material by wet chemical etching.
In accordance with again a further feature of the invention, the base part is coated with the electrically conductive connection material on all sides.
In a preferred embodiment, the connection material of the thin base part coating comprises copper.
In accordance with yet another feature of the invention, the base part is composed of plastic and prefabricated in an injection-molding process.
In accordance with a concomitant feature of the invention, the material of the mask layer comprises tin.
With the above and other objects in view there is also provided, in accordance with the invention, a method of producing an optoelectronic component, which comprises:
covering a base part with a thin coating of electrically conductive connection material by depositing from a liquid, preferably chemically without an external current;
depositing a mask layer on the thin base part coating;
patterning the mask layer and identifying regions of the thin base part coating that are not covered and regions that are covered by the mask;
selectively etching and removing the thin base part coating in the regions that are not covered by the mask; and mounting a radiation-receiving or radiation-emitting semiconductor chip on the base part and electrically connecting the semiconductor chip to the electrically conductive connection material forming at least two electrode terminals of the component.
In other words, a first version of the production method is distinguished by the fact that the base part is covered with a thin coating made of the electrically conductive connection material by means of deposition from a liquid, in particular chemically and without the action of an external electric current flow, the thin coating of the base part is patterned and, in the process, individual regions of the coating, which are electrically insulated from one another, are fabricated, a further thin layer made of an auxiliary material is deposited, by electrodeposition under the action of an external electric current flow, selectively on a number of predetermined regions of the thus fabricated regions of the thin coating, as a result of which the layer thickness of these predetermined regions of the coating is increased, and the unthickened regions of the base part coating are selectively removed by means of etching.
A further method according to the invention is distinguished by the fact that the base part is covered with a thin coating made of the electrically conductive connection material by means of deposition from a liquid, in particular chemically and without the action of an external electric current flow, a mask layer is deposited on the thin base part coating, the mask layer is patterned, as a result of which regions of the base part coating which are not covered and those which are covered by the mask material are identified, and the regions which are not covered by the material of the mask layer are selectively removed by means of etching.
The particular advantages achieved by the invention are that the use of a prefabricated plastic base part, preferably plastic injection-molded part, on which the electrode terminals serving for the electrical contact-making of the component are applied using a patterned coating technique, means that it is possible to produce optocomponents for surface mounting technology (SMT) with smaller structural heights and with essentially low manufacturing costs. On account of flexible process control, the invention makes it possible to produce a wide variety of different designs and electrode terminal forms; a plurality of components in an interconnection, so-called arrays, can be produced in an equally cost-effective and simple manner. A wide range of component modifications can be covered with just one base part. If the component is an LED, for example, the base part is substantially simpler in terms of its configuration than the conventional LED carriers with lead frame and/or with embossed reflector.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an optoelectronic component and method for its production, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.